Local area network of serial intelligent cells

ABSTRACT

A device for coupling first and second bi-directional wired digital data signals to each other and to a data unit, for use with first and second service wire pairs installed at least in part in walls within a building. The first service wire pair concurrently carries the first bi-directional wired digital data signal and a first service signal carried over a first service signal frequency band, using frequency division multiplexing. The first wired digital data signal is carried over a frequency band distinct from the first service signal frequency band. The second service wire pair concurrently carries a second bi-directional wired digital data signal and a second service signal carried over a second service signal frequency band, using frequency division multiplexing. The second wired digital data signal is carried over a frequency band distinct from the second service signal frequency band.

This is a continuation of copending parent application Ser. No.10/178,223, filed Jun. 25, 2002, which itself is a continuation of U.S.patent application Ser. No. 09/123,486 filed Jul. 28, 1998, now U.S.Pat. No. 6,480,510, issued Nov. 12, 2002.

FIELD AND BACKGROUND OF THE INVENTION

The present invention relates to local area networks and, moreparticularly, to local area network topologies based on serialintelligent cells.

Bus Topology

Most prior art local area networks (LAN) use a bus topology as shown byexample in FIG. 1. A communication medium 102 is based on two conductors(usually twisted pair or coaxial cable), to which data terminalequipment (DTE) units 104, 106, 108, 110, and 112 are connected, viarespective network adapters 114, 116, 118, 120, and 122. A networkadapter can be stand-alone or housed within the respective DTE.

This prior art bus topology suffers from the following drawbacks:

1. From the point of view of data communication, the medium can varysignificantly from one installation to another, and hence properadaptation to the medium cannot always be obtained.

2. The bus topology is not optimal for communication, and hence:

a) the maximum length of the medium is limited;

b) the maximum number of units which may be connected to the bus islimited;

c) complex circuitry is involved in the transceiver in the networkadapter;

d) the data rate is limited.

3. Terminators are usually required at the ends of the medium, thuscomplicating the installation.

4. Only one DTE can transmit at any given time on the bus, and all otherare restricted to be listeners.

5. Complex arbitration techniques are needed to determine which DTE isable to transmit on the bus.

6. In case of short circuit in the bus, the whole bus malfunctions, andit is hard to locate the short circuit.

7. Addresses should be associated independently with any networkadapter, and this is difficult to attain with bus topology.

Star Topology

A number of prior art network devices and interconnections summarizedbelow utilize star topology.

The multiplexer is a common item of equipment used in communication,both for local area networks and wide-area networks (WAN's). It is usedin order to provide access to a data communications backbone, or inorder to allow sharing of bandwidth between multiple stations. As shownin FIG. 2, one side of a multiplexer 202 is usually connected to asingle high data rate connection 204 (“highway”), but several suchconnections can also be used. The other side of multiplexer 202 hasmultiple low data rate connections 206, 208, 210, 212, and 214. Theellipsis . . . indicates that additional connections can be made. Eachlow data rate connection uses part of the bandwidth offered by the highdata rate connection. These low data rate connections can be of the sametype or different types, and can have different or identical data rates.The multiplexing technique most commonly used is time-domainmultiplexing (TDM). However, frequency-domain multiplexing (FDM) is alsoused.

A popular multiplexer in use is the voice multiplexer, shown in FIG. 3.A pulse-code modulation (PCM) bus 304 handling 2.048 megabits persecond, containing 30 channels of 64 kilobits per second is connected toone side of a PABX/PBX 302, and up to 30 telephone interfaces 308, 312,and 316 are connected to the other side via connections 306, 310, and314. The ellipsis . . . indicates that additional connections can bemade. In this configuration, each channel in the PCM bus can be switchedor be permanently dedicated to a specific telephone line. An example ofsuch system is disclosed in U.S. Pat. No. 3,924,077 to Blakeslee.

Similarly a small private branch exchange (PABX/PBX), as shown in FIG.4, is widely used (usually in an office or business environment) whereseveral outside lines 403, 404, and 405 are connected to one side of aPABX/PBX 402, and multiple telephones 408, 412, and 416 are connected tothe other side via lines 406, 410, and 414, respectively. The ellipsis .. . indicates that additional connections can be made. The PABX/PBXconnects an outside line to a requesting or requested telephone, andallows connection between telephones in the premises.

In the configurations described above, star topology is used in order toconnect to the units to the multiplexer, which functions as the networkhub. The disadvantages of star topology include the following:

1. A connection between each unit and the network hub is required, andthe wiring required for this connection can involve a lengthy run.

Thus, when adding new unit, an additional, possibly lengthy, connectionbetween the new unit and the network hub must be added.

2. No fault protection is provided: Any short circuit or open circuitwill disrupt service to the affected units.

3. The multiplexer can impose extensive space and power requirements.

Computer Interfaces

Various interface standards have been established in order to allowinteroperability between the PC (personal computer) or workstation andits various connected elements. These standards usually relate to bothmechanical and electrical interfaces, and include industry standardarchitecture (ISA), extended industry standard architecture (EISA),Personal Computer Memory Card Industry Association (PCMCIA), intelligentdrive electronics (IDE), small computer system interface (SCSI), andothers. Each added hardware unit usually utilizes a specific softwaredriver for interoperability with the specific platform. These protocolsare applicable to small distances only, and allow units to be housedwithin or nearby the PC or workstation enclosures. For example,equipping a PC for video capture could involve a plug-in ISA card housedwithin the PC on the motherboard, a video camera connected to the card,and a software driver. This configuration does not allow remote videomonitoring.

Relevant Prior Art

The use of the same wire pair or pairs for both power and datacommunication is well known, and is widely used in telecommunications,from “Plain Old Telephone Service” (“POTS”) to Integrated ServicesDigital Network (ISDN) and broadband services in the local-loopincluding other Digital Subscriber Line (xDSL) technologies. Such aconcept is described, for example, in U.S. Pat. No. 4,825,349 to Marcel,describing using two pairs for such a scheme. A DC-to-DC converter forsuch DC feeding is described, for example, in U.S. Pat. No. 4,507,721 toYamano et al.

The concept of power line communication (PLC) is also widely known.However, in most cases the connection is similar to a LAN environment,in which a single transmitter occupies the entire medium. Examples ofsuch techniques include X-10 and the consumer electronics bus (CEBus,described in the EIA-600 standard). Much of this technology uses complexspread-spectrum techniques in order to accommodate problematic media(characterized by high amounts of noise and interference). Even withsuch improved technologies, however, the data rate obtained isrelatively low.

Prior art in this field includes U.S. Pat. No. 5,684,826 to Ratner, U.S.Pat. No. 5,491,463 to Sargeant et al., U.S. Pat. No. 5,504,454 toDaggett et al., U.S. Pat. No. 5,351,272 to Abraham, U.S. Pat. No.5,404,127 to Lee et al., U.S. Pat. No. 5,065,133 to Howard, U.S. Pat.No. 5,581,801 to Spriester et al., U.S. Pat. No. 4,772,870 to Reyes, andU.S. Pat. No. 4,782,322 to Lechner et al. Other patents can be found inU.S. Class 340/310 (sub-classes A/R and others) and International ClassH04M 11/04.

The concept of using existing telephone wiring also for datacommunication is first disclosed in U.S. Pat. No. 5,010,399 to Goodmanet al., where video signals superimposed over the telephone signals areused. However, the scheme used is of the bus type and has the drawbacksof that topology. Similarly, the idea of data transmission over a publicswitched telephone network (PSTN) using the higher frequency band iswidely used in the xDSL systems, as is disclosed in U.S. Pat. No.5,247,347 to Litteral et al. The patent discloses an asymmetric digitalsubscriber line (ADSL) system. However, only a single point-to-pointtransmission is described over the local-loop, and existing in-housewiring is not discussed, and thus this prior art does not disclose howto configure a full multipoint network. Multiplexing xDSL data and thePOTS/ISDN data uses FDM principles, based on the fact that the POTS/ISDNservices occupy the lower portion of the spectrum, allowing for the xDSLsystem to use the higher bandwidth.

A home bus network using dedicated wiring is disclosed in U.S. Pat. No.4,896,349 to Kubo et al., and a home automation network based on a powerline controller (PLC) is disclosed in U.S. Pat. No. 5,579,221 to Mun.U.S. Pat. No. 4,714,912 to Roberts et al. is the first to suggestcommunicating data over power lines not in bus topology but as‘break-and-insert’. However, only single conductor is used, and thereceivers are all connected again using a bus topology.

In addition, U.S. patent application Ser. No. 08/734,921, Israel PatentApplication No. 119454, and PCT Patent Application No. PCT/IL97/00195 ofthe present inventor disclose a distributed serial control system ofline-powered modules in a network topology for sensing and control.These documents, however, do not disclose a local area network for datacommunications.

The prior art documents mentioned above are representative examples inthe field. Certain applications are covered by more than one issuedpatent.

There is thus a widely recognized need for, and it would be highlyadvantageous to have, a means of implementing a local area network fordata communications which does not suffer from the limitations inherentin the current methods. This goal is met by the present invention.

SUMMARY OF THE INVENTION

The present invention is of a local area network for data communication,sensing, and control based on serially connected modules referred to as“serial intelligent cells” (SIC's). An example of a local area networkof such devices according to the present invention is illustrated inFIG. 7, to which reference is now briefly made. In this example, SIC's700, 702, 704, 706, and 708 are connected by one or more conducting wirepairs (such as a twisted pair 710). This allows chaining, such as SIC700 to SIC 702 to SIC 704. However, SIC 700, SIC 706, and SIC 708,located at the ends are equipped with single connection. SIC 704 isequipped with three connections, and even more connections are possible.A SIC may be interfaced to one or more DTE's, as illustrated by a DTE714 interfaced to SIC 700 and by DTE's 716 and 718 interfaced to SIC704. SIC's need not have an interface, however, as is illustrated by SIC706 and SIC 702. SIC 702, though, serves as a repeater, connecting SIC700 and SIC 704. It is to be noted that the networks according to thepresent invention utilize electrically-conducting media to interconnectthe SIC's. Each electrically-conducting medium connects exactly twoSIC's into a communicating pair of SIC's which communicatebidirectionally and independently of other communicating pairs in thelocal area network. Electrically-conducting media are media whichtransmit signals by conducting electrical current or by propagatingelectrical potential from one point to another. Electrically-conductingmedia include, but are not limited to wires, twisted pair, and coaxialcable. But electrically-conducting media do not include media such asfiber optic lines, waveguides, microwave, radio, and infraredcommunication media.

As noted above, SIC's in a communicating pair communicatebidirectionally. For example, SIC 704 can initiate communication (as asender) to SIC 702 (as a receiver), but SIC 704 can just as wellinitiate simultaneous communication (as a sender) to SIC 700 (as areceiver). Bidirectional communication can take place simultaneously,and herein is taken to be equivalent to “full duplex” communication. Inaddition, as noted above, the communication between the SIC's of acommunicating pair is independent of the communication between the SIC'sof any other communicating pair, in that these communications neitherpreclude nor affect one another in any way. Furthermore, everycommunication between SIC's is a “point-to-point communication”, whichterm herein denotes a communication that takes place between exactly onesender and exactly one receiver. This is in contrast to a bus-basedcommunication, in which there are many (potential) receivers and many(potential) senders. Consequently, in the topology according to thepresent invention, there is automatically a termination in the physicallayer at each end of a connection (a SIC), both simplifying theinstallation and insuring more reliable communication.

The topology according to the present invention is superior to the priorart bus topology in the following ways:

1. There is no physical limit to the number of SIC's which may beinstalled in the network, and hence no physical limit to the number ofDTE's in the network.

2. Point-to-point communication allows higher data rates over greaterdistances.

3. Point-to-point communication requires less complex circuitry than buscircuitry.

4. Several SIC's can transmit and receive simultaneously. For example,SIC 700 can communicate with SIC 702 while SIC 704 communicatessimultaneously with SIC 706.

5. There is no need for arbitration, allowing more efficient utilizationof the network. Furthermore, priorities can be assigned to each SIC or,alternatively, to each specific message to allow the data routing totake care of priorities.

6. Addresses may be assigned by the network.

7. In the case of failure of any conductor or SIC, the network can sensethe fault immediately, and the specific location of the fault (up to thespecific SIC pair) is easily obtained.

Therefore, according to the present invention there is provided a localarea network for data communication, sensing, and control including aplurality of serial intelligent cells interconnected exclusively byelectrically-conducting media into at least one communicating pair,wherein: (a) each of the electrically-conducting media interconnects nomore than two of the serial intelligent cells; (b) each of thecommunicating pair includes one of the electrically-conducting media andexactly two of the serial intelligent cells; (c) each of thecommunicating pair engages in a communication exclusively over theelectrically-conducting media; and (d) each of the communicating pairengages in the communication bidirectionally and independently of thecommunication of any other of the communicating pair.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is herein described, by way of example only, withreference to the accompanying drawings, wherein:

FIG. 1 shows a common prior art LAN bus topology.

FIG. 2 shows a typical prior art multiplexer.

FIG. 3 shows a prior art voice multiplexer (star topology).

FIG. 4 shows a prior art voice exchange configuration (star topology).

FIG. 5 is a block diagram of a SIC for control applications according tothe present invention.

FIG. 6 is a block diagram of a SIC for data communications according tothe present invention.

FIG. 7 shows a LAN topology utilizing the devices of the presentinvention.

FIG. 8 shows an alternative LAN topology utilizing the devices of thepresent invention.

FIG. 9 shows a SIC-based multiplexer—PABX/PBX according to the presentinvention.

FIG. 10 shows a local area network according to the present inventionused as a computer bus extender.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The principles and operation of a local area network according to thepresent invention may be better understood with reference to thedrawings and the accompanying description.

FIG. 5 is a block diagram of a representative SIC 500 for use in controlapplications. A first line interface 502 is a first port for connectingto the previous SIC to receive incoming electrical power and local areanetwork data over electrically-conducting medium 503, which mayoptionally be connected to an electrical power main 501, so that SIC 500may be powered from electrical power main 501. Line interface 502 mayinclude the connector, fuse, lightning arrester and other protectionsuch as noise filters, etc. The incoming power/data signal is fed to afirst power/data splitter/combiner 504, which de-couples the (highfrequency alternating current) data signal from the power. Such apower/data splitter/combiner 504 (denoted for brevity in FIG. 5 as “P/Ds/c”) can be implemented by methods well-known in the art, such as usinga center-tap transformer, or alternatively with active components. Thedata signal is fed to a first modem 506 allowing bidirectionalcommunication, while the power is fed to a power supply 520. The abovescheme assumes that both power and data are carried by the same networkwires (line-powering). FIG. 5 illustrates the case where the SIC isline-powered by alternating current (for example, by the electricalpower main), in which case power/data splitter/combiner 504 is an ACpower/data splitter/combiner, which separates a low-frequencyalternating current power from the higher-frequency data signal.Otherwise, in the case where the SIC is line-powered by direct current,power/data splitter/combiner 504 is a DC power/data splitter/combiner,which separates direct current power from the data signal. In some casesthe line-powering method is not used. For example, power can be carriedby dedicated lines routed in conjunction with the data wiring.Alternatively, the SIC can be locally powered by a local power-supply.In both cases, the power/data splitter/combiner is not required, and thepower lines are directly connected to the SIC power-supply, while thedata connects directly to the modems. Parts of the SIC are shownoptionally housed within an electrical outlet 524, such that connectionsto the local area network as well as to the electrical power mains maybe made from electrical outlet 524. Electrical power from electricaloutlet 524 can be fed to an optional electrical appliance 525. Inaddition, SIC 500 contains an optional electrical power main feed 505which can also power electrical appliances or other devices.

Power-supply 520 provides the required voltages for the SIC and payloadoperation, and also outputs the power to a second Power/datasplitter/combiner 510, for coupling to the next SIC. Communication withthe next (fed) SIC is performed via a second modem 512 connected to asecond line interface 514 via power/data splitter/combiner 510, similarto power/data splitter/combiner 504 as previously described. Lineinterface 514 feeds to electrically-conducting medium 515, whichconnects to the next SIC. Modems 506 and 512 can be standard RS-485,RS-232, or any simple similar data interface transceiver. Alternatively,a complex transceiver can be used for achieving long ranges orhigh-speed operation. CPU and firmware contained in a control block 522control and monitor the unit operation and communication, as well ascontrol the payload through a payload interface 508 interfacing with apayload illustrated by a sensor/actuator 509. For example, interface 508can implement a 4-20 ma standard interface. In a similar way, SIC 500can be used for communication over the power line. To do this, payloadinterface 508 is replaced by a communication port and sensor/actuator509 will be replaced by a DTE.

A SIC for use in data communications as shown in FIG. 6 is substantiallysimilar to that used in control applications as shown in FIG. 5, but hassome specific differences as noted. Also illustrated in FIG. 6 is thecase where the local area network data is carried overelectrically-conducting media which are part of the telephone wiring ofa building. A SIC 600 has a first line interface 602 as a first port forconnecting to the previous SIC to receive incoming power, local areanetwork data, and telephony data via an electrically-conducting medium603. Line interface 602 may include the connector, fuse, lightningarrester and other protection such as noise filters, etc. The incomingpower/telephony/data signal is fed to a first telephony/datasplitter/combiner 604 (denoted for brevity in FIG. 6 as “T/D s/c”),which de-couples the local area network data from the power andtelephony data. Such a telephony/data splitter/combiner 604 can beimplemented by methods well-known in the art, such as using ahigh-pass/low pass filter, or alternatively with active components. Thelocal area network data signal is fed to a first modem 606 allowingbidirectional communication, while the power (DC) is fed to a powersupply 620, and the telephony data is fed to power/telephone interface624.

Power-supply 620 provides the required voltages for the SIC and payloadoperation, and also outputs the power to a second telephony/datasplitter/combiner 610, for coupling to the next SIC. Communication withthe next (fed) SIC is performed via a second modem 612 connected to asecond line interface 614 via telephony/data splitter/combiner 610,similar to telephony/data splitter/combiner 604 as previously described.Line interface 614 connects to an electrically-conducting medium 615,which connects to the next SIC. Modems 606 and 612 can be standardRS-485, RS-232 or any simple similar data interface transceiver.Alternatively, a complex transceiver can be used for achieving longranges or high-speed operation. CPU and firmware contained in a controlblock 622 control and monitor the unit operation and communication, aswell as control the payload through a payload interface 608 interfacingwith a payload 609, which may include sensors and actuators. Forexample, interface 608 can implement a 4-20 ma standard interface. SIC600 also includes an optional power/telephone interface 624, containedfor example in a telephone outlet 625, as well as one or morecommunications interfaces, such as a communication interface 626connected to a DTE 628.

In the case of DC line feeding, the power supply may be equipped with aline reversal function (for example, a diode-based bridge) in order toaccommodate a possible wire reversal.

Note that a SIC can be implemented as single device with all componentparts contained within one enclosure, but does not necessarily have tobe so implemented. In the case of a SIC used for data communications orcontrol applications, the hardware may be optionally divided between theSIC module and the DTE/Payload units. In the case of a SIC used fortelephone applications, the hardware may optionally be divided betweenthe SIC, the DTE payload unit, and the telephone outlet, such astelephone outlet 625, which allows connections to both telephoneservices (such as through a telephone 623) and the local area network(such through DTE 628). Telephone outlet 625 may be a wall outlet orjack. All or part of the SIC may be housed within a telephone outletsuch as telephone outlet 625, if desired. Furthermore, for SIC's usedonly as repeaters, a payload interface is not necessary.

Power/data splitter/combiner 510 (FIG. 5) can use various techniquesknown in the art. Coupling can be implemented, for example, as disclosedin U.S. Pat. No. 4,745,391 to Gajjar. Power-supply 520 (FIG. 5) can beconnected to the network using dedicated adapter or via specific SIC.The payload can also be connected using standard Ethernet or other LANinterface, hence emulating the network using the SIC's. Thisconfiguration makes use of standard interfaces, but operates at higherthroughput and data-rates than a conventional LAN.

SIC Addressing

A SIC can include an address. Addresses of SIC's on the network can beassigned via automatic assignment by the local area network itself byalgorithms known in the art, for example as disclosed in U.S. Pat. No.5,535,336 to Smith et al. Addresses can also be assigned via manualassignment, such as by the setting of mechanical switches on the SICunit. Addresses can also be determined by the DTE connected to the SIC,either by means of higher layers as done in most LAN systems, orphysically be means of the connection to the SIC (such as by addresslines).

SIC Powering

A SIC can receive electrical power locally, via a power source locatednear the SIC. However, one power source may be used to power some or allthe SIC's in the local area network using dedicated power lines. Theselines can be routed with the data communication wires. Alternatively,the same electrically-conducting media (the data communication wires)can be used to carry both electrical power and local area network datato the SIC's, by means of techniques well-known in the art, for exampleas in telephone systems. In such a case, a unit is required for couplingthe power supply to the local area network. This can make use of a SIC(such as SIC 706 in FIG. 7) or in a specific dedicated module. Sinceelectrical power is typically distributed at low frequencies (e.g., 60Hertz), whereas local area network data is typically at a much higherfrequency, electrical power can be combined with local area network datausing frequency-domain multiplexing. A SIC can therefore be powered fromthe electrical power mains, and can also deliver electrical power, asillustrated in FIG. 5 and detailed herein above.

The DTE's, sensors, and actuators connected to the SIC's can also belocally powered from the SIC's, or can use the same power resources viathe same channels as the SIC's. Part or all of a SIC can be housedwithin an electrical outlet so that the electrical outlet allowsconnection to the local area network as well as to electrical power.

Control

Although mainly intended to be used as communication network, the systemaccording to the present invention can also be used as a platform toimplement a sensing, control, and automation system. This is achieved byadding to one or more of the SIC's interfaces to sensors or actuators.The signals received by the sensors are transmitted over the network vialogic contained in the SIC's or in the DTE's, which thereupon operatethe relevant actuators. This automation function can be monitored by oneor more of the DTE'S.

The operation of the control may be associated with data communicatedover the network (for example, sensing the availability of power to aDTE) or may be independent of it, to allow control decisions to be madelocally.

DTE Interface

The DTE interface can be a proprietary interface or any standard serialor parallel interface, such as ITU-T V.35, ITU-T V.24, etc. In addition,a telephone interface (POTS) or ISDN may be used. This can suit intercomor PBX applications.

Fault Protection

The SIC topology described above can be modified to allow for singlefailure correction. In such a case, the SIC's are connected in a networkwith redundant paths, such as a circular topology as shown in FIG. 8. Inthis example, a SIC 800 is connected to a SIC 802, which is in turnconnected to a SIC 804, which is in turn connected to a SIC 806, whichis in turn connected to SIC 800. When connected in such configuration,any single failure in any conductor, such as in conductor pair 810, willnot effect the system operation, as data routing from any SIC to anyother SIC can be achieved via an alternate path. The term “circulartopology” herein denotes the topology of any local area network of SIC'saccording to the present invention which contains at least twocommunication paths between two different SIC's. For example, in FIG. 8,there are two communication paths from SIC 800 to SIC 804: onecommunication path is from SIC 800 to SIC 802 to SIC 804, and the otherpath is from SIC 800 to SIC 806 to SIC 804. Circular topology providesredundant communication paths that increase the immunity of the localarea network to communication faults. It should be noted that thecircular topology according to the present invention, as shown in FIG.8, differs significantly from the well-known “Token Ring topology” ofthe prior art, as discussed following.

Although circular topology as defined herein can be superficiallysimilar to the Token Ring topology, there are major differences betweenthem. One difference is in the data framing. The Token Ring uses thesame frame structure throughout all communication links in the network,and this requires that the same framing must be recognized by all thecells in the network. In the SIC network according to the presentinvention, however, each communication link (between any two connectedSIC's) is totally independent from all other network communication.Hence, a first SIC can communicate with a second SIC using one type offrame structure and protocol, while the same first SIC can communicatewith a third SIC using a different type of frame structure and protocol.

In addition, in a Token Ring network, there is single direction of dataflow at any given time from a single transmitter to one or morereceivers, and usually, the direction of data flow is constant. The SICnetwork according to the present invention, however, does not impose anylimitation on the data flow in any of the communication links. Fullduplex, half duplex or unidirectional communication is possible, and caneven vary from link to link throughout the network. This allows the SICnetwork to support two independent communication routes simultaneously,provided different segments are used. In FIG. 8, for example, SIC 800can communicate with SIC 802 while SIC 804 simultaneously communicatesdifferent data with SIC 806. This capability is not supported by any ofthe other network configurations.

The above differences affect, for example, the vulnerability of therespective networks to faults. In case of single break or short-circuitanywhere in the medium, the Token Ring network will collapse, disablingany further communication in the system. As another example, in thenetwork disclosed in U.S. Pat. No. 4,918,690 to Markkula et al.(hereinafter referred to as “Markkula”), this fault affects the physicallayer by disabling the media's signal-carrying capability. The TokenRing network will not function at all since the data layer functionalitybased on unidirectional transmission will not be supported. In contrast,however, a SIC network according to the present invention, will continueto function fully, except for the specific faulty link itself. All otherlinks continue to function normally. Furthermore, the ability tolocalize the fault is not easily performed either in a Token Ringnetwork or in the Markkula network. In the SIC network according to thepresent invention, however, it is simple and straightforward to tracethe fault to the affected link.

Data Distribution over Electrical Power Lines

An important configuration for a network according to the presentinvention uses the electrical power wiring of a building as acommunication media. This can be used, for example, to implement aninexpensive ‘home LAN’. Typical house mains have a connection to singlefeeder with numerous distribution points and outlets. The principlesaccording to the present invention specify a SIC to be located withineach outlet and at each distribution point. This will allow SIC-basedcommunications network, where communication takes place between eachpair of SIC's connected via the wiring. In such a case it is alsoexpected that the mains will also be used to power the SIC's. Aside fromusing the same wiring media, the electrical distribution and thecommunication system sharing the same mains can be totally decoupled.

Another configuration involves adding the SIC to the Mains wiring atpoints distinguished from the mains outlets. The preferred embodiment,however, consists of using the outlets points for both the electricalsupply and the DTE connection points. This involves replacing allelectrical outlets and distribution points with ‘smart’ outlets, havingboth electrical connections and a communications jack. In addition, suchunit may include visual indicators (e.g. LED's) to show thecommunication status, and may also include switches or other means todetermine the outlet address. Such a communication system could be usedfor applications associated with power distribution, as for example tocontrol the load connected to a specific outlet, for remote on/offoperation of appliances, timing of operations, delayed start,disconnection after pre-set time period, and so forth. Such acommunication system could also be used to monitor the power consumed byspecific outlets, such as for Demand Side Management (DSM) or AutomaticMeter Reading (AMR), allowing remote meter reading.

The above described topology may also apply to existing wiring. Onecommon example may be power wiring to consumers located in differentlocations. Such wiring typically relies on bus topology with taps. Inorder to use SIC technology, the wiring must be broken, and a SICinstalled between both ends.

In a similar manner, a communication network employing the electricalpower wiring of vehicles and vessel can be implemented, such as foraircraft, ships, trains, buses, automobiles, and so forth.

Implementing a Local Communication/Telephone System Using SIC's

In this application, existing telephone wiring (either POTS or ISDN) isused as the electrically-conducting media for the local area network,and is used for both local area network data communication and fortelephony. The term “telephony” herein denotes any telephone ortelephonic communication, including both including voice (POTS) and data(ISDN). Telephone outlets are usually connected in point-to-pointtopology without a distribution point. To set up a network, each outletis replaced with SIC-based outlet. If there are distribution points,these distribution points must also be SIC equipped. This configurationresults in a high-performance LAN between the telephone outlets. Asidefrom sharing the same media, the local area network can be decoupledfrom the telephone system. Alternatively, the local area network and thetelephone system can be combined, such that telephony is digitallyintegrated into the local area network data.

The outside telephone service can be treated according to one of thefollowing alternatives:

1. No telephone support. In this configuration, the connection to thenetwork (usually to the public network) is cut, and the network is fullyinternal, with no external telephone service.

2. Telephone as Payload. In this configuration, the telephone capabilityis retained, and telephony data may be integrated into the datacommunication of the local area network. One of the SIC's (usually theone closest to a public telephone network interface) or other dedicatedmodule interconnects (via the communication interface for example) tothe network interface (NI). This unit emulates a telephone interface tothe NI, so that public network operation is transparent and continues toperform as normal. However, the signals associated with the telephoneinterface, either the voice itself and the control/signaling (onhook/off hook, ringing, etc.) are digitized and transmitted in thenetwork as data stream, as part of the communication taking place in thenetwork. In the SIC's interfaced to telephones, these signals areconverted back to analog (or in any original form) and thus can be usedwith standard telephones. In this case, telephone functionality is fullyretained. However, failure in the communication network may result inloss of the telephone service. This can be improved by means of a systemwhich disconnects the SIC's circuitry and restores the original wiringrouting (this can be easily implemented by relays, which bypass theSIC's upon failure detection, manual intervention, or other relevantoccasion).

3. Communication over POTS or ISDN. In this method, theelectrically-conducting media interconnecting SIC's is the telephonewiring of a building. This method involves the known mechanism ‘POTSSplitting’, currently used in conjunction with xDSL technologies. Thisrequires a filter which separates the low-frequency portion of thespectrum (usually carrying the POTS associated signals and power) fromthe high-frequency portion of the spectrum (used for communication). Insuch an application, the AC/DC units in the SIC are replaced with suchPOTS splitter modules. The low-frequency band (POTS related) is passedtransparently (similar to the power pass), and branched to the telephonejack. The high-frequency band is used for the communication between theSIC's. This combining of high-frequency local area network communicationon the same electrically-conducting media with low-frequency telephonydata is a form of frequency-domain multiplexing.

In the latter two alternatives, each in-wall telephone outlet isreplaced with a SIC based outlet having both a telephone jack and one(or more) communication jacks.

Computer Bus Extender

The SIC network can be used as a computer bus extender, such as an ‘ISAbus extender’, as illustrated in FIG. 10. In this configuration, a SIC1006 is equipped with a computer bus connector 1004 which is connected,for example, to one of the ISA bus slots in a computer 1002, totransport data between the local area network and computer 1002. AnotherSIC 1010, remotely located, also has a computer bus connector 1012, suchas an ISA bus extender. This allows for a transparent ISA buscapability, where the ISA bus data will be transported in bothdirections over electrically-conducting medium 1008. The ellipses ( . .. ) indicate that additional SIC's and electrically-conducting media maybe present in the local area network between SIC 1006 and SIC 1010.Shown as an example, a video frame grabber card 1014 is plugged intocomputer bus connector 1012, and a video camera 1016 is connected tovideo frame grabber card 1014. Normally, video frame grabber card 1014is plugged directly into an ISA bus slot, such as in computer 1002.Here, however, the local area network acts as a bus extender so thatvideo frame grabber 1014 and video camera 1016 can be located remotelyfrom computer 1002. The normal software driver for the ISA bus slot incomputer 1002 can used, since computer 1002 is unaware of the fact thatonly ISA emulation is taking place. This way, the capability of havinggeneral remote PC components and peripherals can be easily achieved.This configuration features the above-described advantages, and thismethod can be used to attain various goals, such as fault protection.Similarly, this method can be used to connect several units remotely toa computer, using different ports in the computer.

Implementing Multiplexers and PABX/PBX Functionality

A network of SIC's may be used to implement a multiplexer or a PABX/PBXfunctionality, as illustrated in FIG. 9. In this example, a SIC 900 isconnected to a high data rate connection, such as PCM bus 916, while SIC902 and SIC 906 are connected to telephones 908, 910, and 912. SIC 904functions as a repeater in this example.

In this example, the local area network functions as a multiplexer,wherein the bandwidth of the high data rate connection (PCM bus 916) ismultiplexed through SIC 900 to SIC 902 and SIC 906, each of which mayuse a different portion of the bandwidth of the high data rateconnection (PCM bus 916). Moreover, by the addition of telephones 908,910, and 912, the local area network of FIG. 9 functions as a voicemultiplexer.

Other Applications of the Invention

A number of applications of the present invention have been discussedabove. Additional applications include, but are not limited to:intercom, PABX/PBX, security systems, video surveillance, entertainmentbroadcasting services, time (clock) distribution, and audio/video signaldistribution. The networks implemented by the present invention canextend locally within a single building or over a neighborhood.

While the invention has been described with respect to a limited numberof embodiments and applications, it will be appreciated that manyvariations, modifications and other applications of the invention may bemade.

1. A device for coupling first and second bi-directional wired digitaldata signals to each other and to a data unit, for use with first andsecond service wire pairs installed at least in part in walls within abuilding, the first service wire pair concurrently carrying the firstbi-directional wired digital data signal and a first service signalcarried over a first service signal frequency band, using frequencydivision multiplexing wherein the first wired digital data signal iscarried over a frequency band distinct from the first service signalfrequency band, and the second service wire pair concurrently carrying asecond bi-directional wired digital data signal and a second servicesignal carried over a second service signal frequency band, usingfrequency division multiplexing wherein the second wired digital datasignal is carried over a frequency band distinct from the second servicesignal frequency band, said device comprising: a single enclosure and,within said single enclosure; a first wiring connector for connectingsaid device to the first service wire pair; a first filter coupled tosaid first wiring connector for passing only the first bi-directionalwired data signal; a first modem coupled to said first filter forcoupling with the first bi-directional wired data signal; a secondwiring connector for connecting said device to the second service wirepair; a second filter coupled to said second wiring connector forpassing only the second bi-directional wired data signal; a second modemcoupled to said second filter for coupling with the secondbi-directional wired data signal; a multiport unit coupled to said firstand second modems and operative to allow the first and secondbi-directional wired digital data signals to be independent of oneanother; a standard data interface coupled to the multiport unit forcoupling a standard data interface signal to at least one of the firstand the second bi-directional wired data signals; and a data portcoupled to the standard data interface and couplable to a data unit forcoupling to the standard data interface signal thereto, wherein saiddevice is addressable.
 2. The device according to claim 1, wherein thefirst service wire pair is a power line, the first service signal is anAC power signal and the first bi-directional wired digital data signalis PLC based.
 3. The device according to claim 2, wherein: the firstfilter is a low pass filter for passing only the AC power signal; andsaid device further comprises a power supply coupled to said firstfilter for receiving the AC power signal for powering at least part ofsaid device.
 4. The device according to claim 1, wherein the firstservice wire-pair is a coaxial cable.
 5. The device according to claim1, wherein one of the first and second wire pairs carries a powersignal, and the device further comprises a power supply coupled to thepower signal to be powered therefrom, for powering at least part of saiddevice.
 6. The device according to claim 5, wherein said device isfurther operable to power a connected unit.
 7. The device according toclaim 6, wherein said device is further operative to control the powerprovided to the connected unit.
 8. The device according to claim 6,wherein said device is further operative to monitor the power providedto the connected unit.
 9. The device according to claim 1, wherein thefirst service wire pair is a telephone wire pair and the first servicesignal is one of a POTS telephone signal and an ISDN telephone signal.10. The device according to claim 9, wherein the first bi-directionalwired digital data signal is xDSL based.
 11. The device according toclaim 1, for coupling to multiple data units, wherein said devicefurther comprises: an additional standard data interface coupled to themultiport unit for coupling an additional standard data interface signalto one of the first and the second bi-directional wired data signal; andan additional data port coupled to the additional standard datainterface and couplable to a data unit for coupling to the additionalstandard data interface signal thereto.
 12. The device according toclaim 11, wherein the additional standard data interface is distinctfrom the first data interface.
 13. The device according to claim 1,further comprising means for mounting said device on a wall.
 14. Thedevice according to claim 13, wherein said device is included in anoutlet.
 15. The device according to claim 14, wherein the outlet is oneof a telephone outlet and a power outlet.
 16. The device according toclaim 1, wherein said device has an address that is at least in partbased on a manually assigned address.
 17. The device according to claim1, wherein said device has an automatically assigned address.
 18. Thedevice according to claim 1, wherein said device has an address that isat least in part based on data from a data unit coupled to said device.19. The device according to claim 1, wherein said device is furtheroperative to couple a service unit to the first service signal, and saiddevice further comprises: a service filter coupled to the first wiringconnector for passing only the first service signal; and a serviceconnector coupled to said service filter and couplable to a serviceunit, for coupling the service unit to the first service signal.
 20. Thedevice according to claim 19, wherein the service unit is one out of atelephone unit and an AC powered appliance.
 21. The device according toclaim 1, wherein the first service signal is distinct from the secondservice signal.
 22. The device according to claim 1, further operativeto couple the first and second service signal, the device furthercomprising: a first service filter coupled to the first wiring connectorfor passing only the first service signal, a second service filtercoupled between the first service filter and the second wiring connectorfor passing only the second service signal for coupling together thefirst and the second service signals.
 23. The device according to claim1, wherein the first bi-directional wired digital data signal comprisesa digitized telephone signal, said device is further operative to couplean analog telephone unit to the digitized telephone signal, and saiddevice further comprises: a telephone connector connectable for couplingthe analog telephone unit to the digitized telephone signal , and meansfor converting between the analog telephone unit signal and thedigitized telephone signal.
 24. The device according to claim 1, whereinthe standard data interface is operative to interface with packet basedor Ethernet based signals.
 25. A network for carrying data and servicesignals, said network comprising: first and second nodes and first andsecond service wiring segments, wherein said first service wiringsegment comprises a first wire pair installed at least in part in wallswithin a building, said first wire pair concurrently carrying a firstbi-directional wired digital data signal and a first service signalcarried over a first service signal frequency band, using frequencydivision multiplexing wherein the first wired digital data signal iscarried over a frequency band distinct from the first service signalfrequency band, and wherein the first bi-directional digital data signalcarries distinct first and second digital data streams, said secondservice wiring segment comprises a second wire pair installed at leastin part in walls within a building, the wire pair concurrently carryinga second packet-based wired digital data signal and a second servicesignal carried over a second service signal frequency band, usingfrequency division multiplexing wherein the second wired digital datasignal is carried over a frequency band distinct from the second servicesignal frequency band, and wherein the second bi-directional digitaldata signal carries a third digital data stream; said first node isconnected to said first and second wiring segments, couples the firstand second wired digital data signals, and is operative to pass onlydata in the first digital data stream to the third digital data stream;said second node is connected to said second wiring segment, isconnectable to a data unit, and is operative to couple the data unit tothe second wired digital data signal, and said first node isaddressable.
 26. The network according to claim 25, wherein one of saidfirst and second service wiring segments is a power line segmentcarrying an AC power signal as the service signal of that service wiringsegment, and a power line communication based wired digital data signalas the bi-directional digital data signal.
 27. The network according toclaim 26, wherein one of said first and second nodes comprises: a filtercoupled to the to the wiring segment carrying the AC power signal forpassing only the AC power signal; and a power supply coupled to saidfilter to be fed by the AC power signal for powering at least part ofthe one of the nodes connected to the wiring segment carrying the ACpower signal.
 28. The network according to claim 25, wherein one of saidfirst and second service wiring segments is a coaxial cable.
 29. Thenetwork according to claim 25, wherein one of said first and secondwiring segments carries a power signal as a respective one of theservice signals, and one of said first and second nodes furthercomprises a power supply coupled to said power signal to be poweredtherefrom, for powering at least part of said one of said first andsecond nodes.
 30. The network according to claim 29, wherein said one ofsaid first and second nodes is further operable to power a connectedunit.
 31. The network according to claim 30, wherein said one of saidfirst and second nodes is further operative to control or monitor thepower provided to the connected unit.
 32. The network according to claim25, wherein one of said first and second service wiring segments is atelephone wire pair and the service signal carried by said one of saidfirst and second service wiring segments is a POTS telephone signal oran ISDN telephone signal.
 33. The network according to claim 32, whereinone of the first and second wired digital data signals is xDSL based.34. The network according to claim 25, for coupling to multiple dataunits, wherein one of said first and second nodes comprises: a standarddata interface coupled to one of the first and second bi-directionalwired data signals, and a data port coupled to said standard datainterface and couplable to a data unit for coupling the data unit to oneof the first and second bi-directional wired data signals.
 35. Thenetwork according to claim 34, wherein multiple distinct data interfacesare provided in one of the first and second nodes.
 36. The networkaccording to claim 25, wherein one of said first and second nodes ismounted on a wall.
 37. The network according to claim 36, wherein saidone of said first and second nodes is included in an outlet.
 38. Thenetwork according to claim 37, wherein the outlet is one of a telephoneoutlet and a power outlet.
 39. The network according to claim 25,wherein said first node has an address that is at least in part based ona manually assigned address.
 40. The network according to claim 25,wherein said first node has an automatically assigned address.
 41. Thenetwork according to claim 25, wherein said first node has an addressthat is at least in part based on data from a data unit coupled to saidfirst node.
 42. The network according to claim 25, wherein one of saidfirst and second nodes is further operative to couple a service unit toone of the first and second service signals, and said one of said firstand second nodes comprises: a service filter coupled to the firstservice wiring segment for passing only the first service signal; and aservice connector coupled to said service filter and couplable to aservice unit, for coupling the service unit to one of the servicesignals.
 43. The network according to claim 42, wherein the service unitis a telephone unit or an AC powered appliance.
 44. The networkaccording to claim 25, wherein the first service signal is distinct fromthe second service signal.
 45. The network according to claim 25,wherein said first node comprises: a first service filter coupled tosaid first wiring segment for passing only the first service signal; anda second service filter coupled between said first service filter andsaid second wiring segment for passing only the second service signal,and wherein the first and the second service signals are coupled to eachother.
 46. The network according to claim 25, wherein one of the firstand second bi-directional wired digital data signals comprises adigitized telephone signal, and one of the first and second nodes isfurther operative to couple a telephone unit to the digitized telephonesignal.
 47. The network according to claim 46, wherein the telephoneunit is a POTS telephone unit or a digital telephone unit.
 48. Thenetwork according to claim 25, wherein one of the first and seconddigital data signals is packet based.
 49. The network according to claim25, wherein the first digital data signal carries multiple digitizedtelephony signals, and the second digital data signal carried at leastone digitized telephony signal.
 50. A device for coupling a telephoneunit to an analog telephone signal and for coupling a data unit to abi-directional wired digital data signal, for use with a telephone wirepair installed at least in part in walls within a building, the wirepair concurrently carrying a power signal, the bi-directional wireddigital data signal and the analog telephone signal carried over atelephone signal frequency band, using frequency division multiplexing,wherein the wired digital data signal is carried over a frequency banddistinct and higher than the telephone signal frequency band, whereinsaid device comprises: a first connector for connecting said device tothe telephone wire pair; a high pass filter coupled to said firstconnector for passing only the bi-directional wired digital data signal;a modem coupled to said high pass filter for coupling with thebi-directional digital wired data signal; a data port coupled to saidmodem and couplable to a data unit, for coupling the data unit to thebi-directional digital wired data signal; a low pass filter coupled tosaid first connector for passing only the analog telephone signal; atelephone connector coupled to said low pass filter and connectable to atelephone unit, for coupling the telephone unit to the analog telephonesignal; and a power supply coupled between said first connector and saidmodem to be powered by the power signal for powering said modem.
 51. Thedevice according to claim 50, wherein said device is addressable. 52.The device according to claim 50, wherein the power signal is a DCsignal.
 53. The device according to claim 50, wherein the power signalis an AC signal.
 54. The device according to claim 53, wherein the powersignal has a frequency distinct from the data and telephone signals. 55.The device according to claim 50, wherein the data port is operative tocouple to a packet based signal.
 56. The device according to claim 50,wherein said device is further operative to power a connected device.57. The device according to claim 56, wherein said device is furtheroperative to power a connected data unit.
 58. The device according toclaim 50, wherein said device is further attachable to a wall.
 59. Thedevice according to claim 50, wherein said device is at least in parthoused within a telephone outlet.
 60. The device according to claim 50,wherein the digital data signal is DSL based.